package org.apache.lucene.search;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;
import org.apache.lucene.index.*;

/**
 * Position of a term in a document that takes into account the term offset within the phrase. 
 */
final class PhrasePositions {
    int doc; // current doc
    int position; // position in doc
    int count; // remaining pos in this doc
    int offset; // position in phrase
    final int ord; // unique across all PhrasePositions instances
    TermPositions tp; // stream of positions
    PhrasePositions next; // used to make lists
    PhrasePositions nextRepeating; // link to next repeating pp: standing for same term in different query offsets

    PhrasePositions(TermPositions t, int o, int ord) {
        tp = t;
        offset = o;
        this.ord = ord;
    }

    final boolean next() throws IOException { // increments to next doc
        if (!tp.next()) {
            tp.close(); // close stream
            doc = Integer.MAX_VALUE; // sentinel value
            return false;
        }
        doc = tp.doc();
        position = 0;
        return true;
    }

    final boolean skipTo(int target) throws IOException {
        if (!tp.skipTo(target)) {
            tp.close(); // close stream
            doc = Integer.MAX_VALUE; // sentinel value
            return false;
        }
        doc = tp.doc();
        position = 0;
        return true;
    }

    final void firstPosition() throws IOException {
        count = tp.freq(); // read first pos
        nextPosition();
    }

    /**
     * Go to next location of this term current document, and set 
     * <code>position</code> as <code>location - offset</code>, so that a 
     * matching exact phrase is easily identified when all PhrasePositions 
     * have exactly the same <code>position</code>.
     */
    final boolean nextPosition() throws IOException {
        if (count-- > 0) { // read subsequent pos's
            position = tp.nextPosition() - offset;
            return true;
        } else
            return false;
    }

    /** for debug purposes */
    @Override
    public String toString() {
        String s = "d:" + doc + " o:" + offset + " p:" + position + " c:" + count;
        if (nextRepeating != null) {
            s += " rpt[ " + nextRepeating + " ]";
        }
        return s;
    }
}
